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Abstract

A detailed review of existing flying height or head disk spacing testing techniques has
been made, and in-depth analyses of the working principles of the currently popular
optical interferometry flying height testing methods are presented with simulation
results. A new dual-beam normal incidence polarisation inteferometry method is then
proposed. One advantage of this dual-beam polarisation interferometry is that it can be
used for both the direct spacing measurement (DSM) method and relative displacement
measuring (RDM) method. The RDM method is a good way to measure the head-disk
spacing and the slider pitch or roll when a real magnetic disk is used for testing. The
DSM method has the advantage that the absolute head-disk spacing can be observed and
measured directly, especially in the case where it is difficult for the light beam to 'spot'
the back surface of the head-slider. When used for the DSM method, the flying height
can be measured down to contact without losing sensitivity. Slider pitch or roll can also
be measured using the phase information. Another advantage of this polarisation
interferometry is that, when used for the DSM method, with the measured intensity and
phase information, the optical constants of the slider material can be determined, which
is necessary to determine the flying height. By investigation of the application limits
and potential problems of the intensity interferometry method, an improved intensity
interferometry method is also proposed by using phase-shifting technique to improve
the sensitivity of this method when the head-disk spacing is below 10 nm and near
contact. An experimental testing system has been built to test the capability and
effectiveness of the proposed interferometry methods. Experimental results are
presented which show good agreement with the results gained from theoretical analyses
and simulation.

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All items in PEARL are protected by copyright law.
Author manuscripts deposited to comply with open access mandates are made available in accordance with
publisher policies. Please cite only the published version using the details provided on the item record or document.
In the absence of an open licence (e.g. Creative Commons), permissions for further reuse of content should be
sought from the publisher or author.